Nature of Science
A student is using an electronic balance to determine how much matter is in a sample of salt. What is the property they are measuring AND what is the units they should use?
mass (grams)
You hold a cold metal spoon in a cup of hot chocolate. This is the direction the thermal energy moves.
From the hot chocolate to the spoon.
A student is looking at a container of pure Iron (Fe). This substance is classified as an element because...
It contains only one type of atom.
A student leaves a bicycle outside and it begins to rust.
What observation did the student make to determine this is a chemical change?
color change (formation of a new substance)
A student uses a ruler to find that a wooden block is 12 centimeters long. Identify the property being measured and the standard unit used.
Ruler, centimeters
In a study testing if different types of floor wax make a floor more slippery, a student uses the same type of shoes and the same person to walk across each waxed surface.
These two factors are known as...
constants (controlled variables)
A scientist has three samples of gold:
Sample X is 10°C
Sample Y is 100°C
Sample Z is 500°C
Which sample has the highest kinetic energy?
Sample Z
Look at the chemical formula for sodium acetate:
NaC2H3O2.
What is the total number of atoms in this molecule?
8
NaC2H3O2
(1 Na, 2 C, 3 H, 2 O)
You take a block of wood and chop it into smaller pieces for a fire.
Why is this considered a physical change?
It is still wood, no new substance is formed.
It is only being cut into smaller pieces.
On a freezing winter morning, a basketball left outside feels "flat" and slightly smaller. This happened because the air molecules inside the ball did these two things.
Decreased kinetic energy (moved slower)
and
Became more dense (moved closer together)
A scientist observes that a substance smells like rotten eggs and has a fuzzy texture.
This type of observation is known as...
Qualitative Observation
On a hot summer day, the air inside a car tire gets warmer. What happens to the motion of the air molecules inside the tire?
It moves more quickly (motion increases in speed)
In the equation
C2H4O2+NaHCO3→NaC2H3O2+H2O+CO2,
What are the substances on the RIGHT side called?
products
While cooking, a student notices that mixing two room-temperature liquids causes the bowl to feel very hot.
This is evidence of what type of change?
Chemical Change/Reaction (temperature change)
Look at the chemical formula for Sodium Bicarbonate:
NaHCO3
Identify the total number of elements present in this compound AND the total number of oxygen atoms.
NaHCO3
4 elements (Na, H, C O)
3 oxygen atoms
A student wants to see if the steepness of a ramp affects how far a toy car rolls. In this experiment, the distance the car rolls is what variable?
Dependent Variable
A hot air balloon rises into the sky because the air inside the balloon is heated, causing the molecules to spread out and cause the DENSITY to become...
LESS dense
During a reaction, the atoms of the reactants do not disappear; instead, they do this to form new products.
Rearrange
(break down and form new bonds/molecules/compounds)
When you boil a pot of water, bubbles form.
This is a physical change rather than chemical because...
There is only a change of state (phase change) from liquid to gas (bubbles = water vapor). No new substance is formed.
A scientist is studying three samples of copper:
Sample 1 is 20ºC
Sample 2 is 50ºC
Sample 3 is 90ºC
Describe the kinetic energy and molecular motion (speed) of Sample 1 compared to Sample 3.
Sample 1 has LOWER kinetic energy and the molecules are moving SLOWER
To find the volume of a toy dinosaur, a student fills a graduated cylinder to 50 mL. After submerged, the water rises to 63 mL.
What is the property they are measuring and the final volume of the toy?
Volume (13 mL)
If a student draws a model of liquid water vs. ice, the molecules in the liquid water model should be shown...
HINT: How would you draw the molecules AND show their speed/motion?
moving faster and spread further apart
A student has a tank of Hydrogen gas (H2). Even though there are two atoms, it is not a compound because...
The atoms are the same type of element
A chef mixes baking soda and lemon juice in a bowl to make a cake rise. She notices the mixture begins to bubble and fizz, and the temperature of the bowl drops. Identify the specific evidence of a chemical reaction in this scenario and explain what is happening to the atoms of the ingredients.
Evidence of Chemical Reaction:
Gas production (fizzing) and Temperature Change
The atoms are rearranging by breaking existing chemical bonds and forming new ones to create new substances.
A student performs a reaction using this equation:
Acetic Acid + Sodium Bicarbonate → Sodium Acetate + Water + Carbon Dioxide (gas)
Identify which substances are the REACTANTS and the specific evidence from the products that a chemical reaction occurred.
Acetic Acid and Sodium Bicarbonate
A chemical reaction occurred because carbon dioxide was formed, which was a gas (bubbling/fizzing)