Chemistry test 1

the ability to make accurate observations

Edmond Locard

a compound is a mixture of elements like water (H₂O)

something that when changed cannot return to the same state.

Example flammability

Determine the nature of the problem

Collect and analyze all relevant data

Form a hypothesis (educated guess) as to what happened

Test the hypothesis

if Hypothesis holds up to testing you're finished

if not go back to step 2

1- Determine Problem

2- Collect/ analyze relevant data

3- Hypothesis (educated guess)

4- Test Hypothesis

5- If Hypothesis holds test finished if not go to step 2

1 - zeros located between nonzero numbers are significant (i.e. 101 - 3 sig figures)

2 - Zeros at beginning of number containing decimal are not significant (i.t. 0.015 - 2 sig figures)

3 - Zeros at the end of a number containing a decimal point are significant (i.e. 25.20 - 4 sig figures)

4 - Zeros at the end of a number not containing decimal are ambigous ( i.e. 100 has at least 1 significant figure but can have up to 3)

Accuracy - how close they are to the truth

Precision - how precise are the estamites (how similar they are to each other)

When something is changed but can come back to original state...

example Ice melting... I can turn it to ice again.

Solid

Liquid

Gas

Particles are in close proximity and fixed position, hard to compress

particles are still fairly close,

hard to compress

volume is constant, shape is not

large disctances between particles

always fills volume and shape of container they are in

compressable

Physical changes do not affect identity of the substance

Chemical change changes the identity of substance

1 - Weigh object

2 - submerge in graduated cylinder containing known amount of water

3 - Record how much volume has changed

4 - difference between beginning volume and end volume is volume of object.

5- D=M/V - Divide weight of object by volume to get density

1 - He wrote properties of known elements on card

2 - then arranged them so that there were logical repeating patterns in properties of elements

3 - One of strengths of his arrangement was that he left gaps