Introduction to Chemistry

I. Chemistry is the study of all matter

Matter and it’s Properties Composition of Matter Chemistry is “lego-science.” Millions of legos form very complex structures, but the basic building block is an individual lego. Atoms – The smallest unit of an element that maintains the properties of that element. So it also is with matter, all of the complex structures that we see around us are composed of basic building blocks. What are these called? Envision a huge box of legos, all the same color, when we have the same type of atoms all grouped together, what do we smart science types call this? Element – A pure substance made of only one kind of atom.

Elements Gold Silver Hydrogen Oxygen

Most substances on earth are not pure Elements combine to form molecules –Salt (sodium & chlorine) –Water (hydrogen & oxygen) –Ozone (2 or 3 oxygen atoms together

________________ - two or more atoms bonded together. Can have the same type of atoms or different types of atoms. Molecules

Matter and it’s Properties Matter: Mass, Weight and Volume Matter is the basis of most of what we see, feel and sense. What matter ISN’T: Matter is not the space that an object takes up. This is the volume of the object. While matter has volume, volume is NOT matter. Matter is simply the amount of material (that is atoms/molecules) that a substance is composed of. All matter takes up space (has volume) and has mass….

Matter and it’s Properties Matter: Mass, Weight, and Volume So to determine the mass of a substance I simply need to “weigh” it right? No - Weight and mass are two different things. Mass – The measure of the amount of matter in a substance. Mass is constant, it doesn’t change depending on your position. Weight is a force, it depends on mass AND gravitational pull or acceleration.

Your weight on other worlds

What is mass? Mass is the amount of matter in an object Mass is constant

Weight The measure of the force of gravity on the mass of an object Weight changes with gravity

Weight formula 1 kg = 2.2 pounds Weight is mass times gravity –Gravity (g) =9.8 m/s round to 10 Weight= Mass x Gravity – W= m x g Practice:

Question 1 The strength of gravity at the Earth’s surface is 10 Newtons per kilogram. Calculate the weight of a car with a mass of 1500 kg. W= M X G W= 1500kg X 10 N/kg W= Newtons

Question 2 The strength of gravity on the moon is 1.6 Newtons per kilogram. If an astronaut’s mass is 80 kg on Earth, what would the mass be on the Moon? 80kg because the mass is constant. If the mass is 80 kg on Earth then it will be 80kg on the moon.

What is the difference between weight and mass? –Weight is the measure of gravity on an object’s mass

COMPARE AND CONTRAST MASS vs. WEIGHT Amount Depends on gravity Does not depend on gravity Weight=mass x gravity Constant Not constant

What about volume? If two things weigh the same do they have the same volumes? Can two things with the same mass have different volumes?

Volume – the amount of space that matter in an object occupies

Measuring Volume Top Image: Bottom Image: 1. Graduated cylinders can be used to find the volume of liquids and other objects. Read the measurement based on the bottom of the meniscus or curve. When using a real cylinder, make sure you are eye-level with the level of the water. What is the volume of water in the cylinder? _____mL What causes the meniscus? A concave meniscus occurs when the molecules of the liquid attract those of the container. The glass attracts the water on the sides. 43 the water molecule are attracted to the glass molecules

Measuring Liquid Volume Images created at What is the volume of water in each cylinder? Pay attention to the scales for each cylinder

Measuring Solid Volume Click here for an online activity about volumeClick here for an online activity about volume. Choose Lessons  Volume & Displacement 10 cm 9 cm 8 cm We can measure the volume of regular object using the formula length x width x height. _____ X _____ X _____ = _____ n/syllabus/unit14/new/testingmain1.htm We can measure the volume of irregular object using water displacement. Amount of H 2 O with object = ______ About of H 2 O without object = ______ Difference = Volume = ______

Determine the volume of this cube. 5.7 cm

The answer is … Volume = length x width x height l = 5.7 cm w = 5.7 cm h = 5.7 cm V = 5.7 cm x 5.7 cm x 5.7 cm V = cm 3

How do you find the volume of a solid using water displacement? –Place water in the graduated cylinder, drop in the solid object, measure the new water level, subtract

Let’s look back at the questions… If two things weigh the same do they have the same volumes?

What about volume? Can two things with the same mass have different volumes?

Newton’s Laws of Motion

Background Sir Isaac Newton ( ) an English scientist and mathematician famous for his discovery of the law of gravity also discovered the three laws of motion. He published them in his book Philosophiae Naturalis Principia Mathematica (mathematic principles of natural philosophy) in Today these laws are known as Newton’s Laws of Motion and describe the motion of all objects on the scale we experience in our everyday lives.

“ If I have ever made any valuable discoveries, it has been owing more to patient attention, than to any other talent.” -Sir Isaac Newton

Newton’s Laws of Motion 1. An object in motion tends to stay in motion and an object at rest tends to stay at rest unless acted upon by an unbalanced force. 2. Force equals mass times acceleration (F = ma). 3. For every action there is an equal and opposite reaction.

Newton’s First Law An object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an unbalanced force.

Newtons’s 1 st Law and You Don’t let this be you. Wear seat belts. Because of inertia, objects (including you) resist changes in their motion. When the car going 80 km/hour is stopped by the brick wall, your body keeps moving at 80 m/hour.

What does this mean? Basically, an object will “keep doing what it was doing” unless acted on by an unbalanced force. If the object was sitting still, it will remain stationary. If it was moving at a constant velocity, it will keep moving. It takes force to change the motion of an object.

What is meant by unbalanced force? If the forces on an object are equal and opposite, they are said to be balanced, and the object experiences no change in motion. If they are not equal and opposite, then the forces are unbalanced and the motion of the object changes.

Some Examples from Real Life Two teams are playing tug of war. They are both exerting equal force on the rope in opposite directions. This balanced force results in no change of motion. A soccer ball is sitting at rest. It takes an unbalanced force of a kick to change its motion.

1 st Law Once airborne, unless acted on by an unbalanced force (gravity and air – fluid friction), it would never stop!

1 st Law Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever.

Newton’s First Law is also called the Law of Inertia Inertia: the tendency of an object to resist changes in its state of motion The First Law states that all objects have inertia. The more mass an object has, the more inertia it has (and the harder it is to change its motion).

More Examples from Real Life A powerful locomotive begins to pull a long line of boxcars that were sitting at rest. Since the boxcars are so massive, they have a great deal of inertia and it takes a large force to change their motion. Once they are moving, it takes a large force to stop them. On your way to school, a bug flies into your windshield. Since the bug is so small, it has very little inertia and exerts a very small force on your car (so small that you don’t even feel it).

If objects in motion tend to stay in motion, why don’t moving objects keep moving forever? Things don’t keep moving forever because there’s almost always an unbalanced force acting upon it. A book sliding across a table slows down and stops because of the force of friction. If you throw a ball upwards it will eventually slow down and fall because of the force of gravity.

In outer space, away from gravity and any sources of friction, a rocket ship launched with a certain speed and direction would keep going in that same direction and at that same speed forever.

Newton’s Second Law The net force of an object is equal to the product of its mass and acceleration, or F=ma. Acceleration: a measurement of how quickly an object is changing speed.

What does F = ma mean? Force is directly proportional to mass and acceleration. Imagine a ball of a certain mass moving at a certain acceleration. This ball has a certain force. Now imagine we make the ball twice as big (double the mass) but keep the acceleration constant. F = ma says that this new ball has twice the force of the old ball. Now imagine the original ball moving at twice the original acceleration. F = ma says that the ball will again have twice the force of the ball at the original acceleration.

More about F = ma If you double the mass, you double the force. If you double the acceleration, you double the force. What if you double the mass and the acceleration? (2m)(2a) = 4F Doubling the mass and the acceleration quadruples the force. So... what if you decrease the mass by half ? How much force would the object have now?

What does F = ma say? F = ma basically means that the force of an object comes from its mass and its acceleration. Something very small (low mass) that’s changing speed very quickly (high acceleration), like a bullet, can still have a great force. Something very small changing speed very slowly will have a very weak force. Something very massive (high mass) that’s changing speed very slowly (low acceleration), like a glacier, can still have great force.

2 nd Law

The net force of an object is equal to the product of its mass and acceleration, or F=ma.

2 nd Law When mass is in kilograms and acceleration is in m/s/s, the unit of force is in newtons (N). One newton is equal to the force required to accelerate one kilogram of mass at one meter/second/second.

2 nd Law (F = m x a) How much force is needed to accelerate a 1400 kilogram car 2 meters per Write the formula F = m x a Fill in given numbers and units F = 1400 kg x 2 meters per second Solve for the unknown 2800 kg-meters/second or 2800 N

2 nd Law (F = m x a) What acceleration will result when a 12 N net force applied to a 3 kg object? Write the formula F = m x a Fill in given numbers and units 12N = 3 kg x a meters per second Solve for the unknown 12N = 3 kg x 4 meters per second

Check Your Understanding 1. What acceleration will result when a 12 N net force applied to a 3 kg object? 12 N = 3 kg x 4 m/s 2. What acceleration will result when a 12N net force applied to a 6 kg object? 12 N = 6 kg x 2 m/s 3. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s 2. Determine the mass. 16 N = 3.2 kg x 5 m/s

If mass remains constant, doubling the acceleration, doubles the force. If force remains constant, doubling the mass, halves the acceleration.

Newton’s 2 nd Law proves that different masses accelerate to the earth at the same rate, but with different forces. We know that objects with different masses accelerate to the ground at the same rate. However, because of the 2 nd Law we know that they don’t hit the ground with the same force. F = ma 98 N = 10 kg x 9.8 m/s/s F = ma 9.8 N = 1 kg x 9.8 m/s/s

Newton’s Third Law For every action there is an equal and opposite reaction.

What does this mean? For every force acting on an object, there is an equal force acting in the opposite direction. Right now, gravity is pulling you down in your seat, but Newton’s Third Law says your seat is pushing up against you with equal force. This is why you are not moving. There is a balanced force acting on you– gravity pulling down, your seat pushing up.

Think about it... What happens if you are standing on a skateboard or a slippery floor and push against a wall? You slide in the opposite direction (away from the wall), because you pushed on the wall but the wall pushed back on you with equal and opposite force. Why does it hurt so much when you stub your toe? When your toe exerts a force on a rock, the rock exerts an equal force back on your toe. The harder you hit your toe against it, the more force the rock exerts back on your toe (and the more your toe hurts).

Other examples of Newton’s Third Law The baseball forces the bat to the left (an action); the bat forces the ball to the right (the reaction).

3 rd Law Consider the motion of a car on the way to school. A car is equipped with wheels which spin backwards. As the wheels spin backwards, they grip the road and push the road backwards.

3 rd Law The reaction of a rocket is an application of the third law of motion. Various fuels are burned in the engine, producing hot gases. The hot gases push against the inside tube of the rocket and escape out the bottom of the tube. As the gases move downward, the rocket moves in the opposite direction.

Review Newton’s First Law: Objects in motion tend to stay in motion and objects at rest tend to stay at rest unless acted upon by an unbalanced force. Newton’s Second Law: Force equals mass times acceleration (F = ma). Newton’s Third Law: For every action there is an equal and opposite reaction.

Vocabulary Inertia: the tendency of an object to resist changes in its state of motion Acceleration: a change in velocity a measurement of how quickly an object is changing speed, direction or both Velocity: The rate of change of a position along a straight line with respect to time Force: strength or energy